Extrusion limit and clearance
Under the action of medium pressure, the O ring will deform and flow to the gap position to achieve the sealing effect. With the increase of the pressure, the O type ring is deformed more and the stress is increased, thus a tighter seal is obtained. Under the condition that the O ring is subjected to high pressure, it will be squeezed into the gap, resulting in failure of the seal. It is recommended to use high hardness anti extrusion ring, such as PTFE or hard rubber material. In the application of static sealing, the groove design can be modified to achieve higher pressure without using the retainer ring. When designing, we should pay attention to make the gap as small as possible.
The size of the extrusion limit depends on the hardness, working pressure and groove clearance of the O ring. The radial clearance of the O ring groove must be kept within a certain radial clearance. If the tolerance is too large, the O ring will be extruded from the gap. The radial clearance between the allowed sealing elements depends on the system pressure, the section diameter of the O ring and the hardness of the O ring.
When the pressure is greater than 5Mpa and the inner diameter of the O ring is greater than 50mm, and the pressure is greater than 10Mpa and the inner diameter is less than 50mm, we recommend the use of the retainer ring.
Because of the excellent anti extrusion ability and good dimensional stability, the O ring of polyurethane material can adopt larger clearance